Slack-thread-controlling device for sewing-machines.



Patented July l6, l90l.

, W. GROTHE.

SLACK THREAD CONTROLLING DEVICE FOR SEWING MACHINES.

(Application filed Feb. 9, 1901. (No Model.) 2 Sheets-$heet l.

No. 678,660. Patented iuly l6, I90l. W. GBUTHE.

SLACK THREAD CONTROLLING DEVICE FOR SEWING MACHINES- (N M d (Application filed Feb. 9, 1901.)

2 Sheets-Shoat 2.

IQin eases v i 'f' tries.

NILLIAM GROTHE, OF CLEVELAND, OHIO, ASSIGNOR TO THE WHITE SEWING MACHINE COMPANY, OF SAME PLACE.

SLACK-THREAD-CONTROLLING DEVICE FOR SEWING-MACHINES.

SPECIFICATION forming part of Lettersfatent No.'678,660, dated July 16, 1901.

Application filed February 9, 1901. Serial No. 46,640. on; model.)

To aZZ whom it may concern.-

Be it known that I, WILLIAM GRorHE, a citizen of the United States, residing at Cleveland, in the county of Ouyahoga and State of Ohio, have invented a certain new and useful Improvement in Slack-Thread-Controlling Devices for Sewing-Machines, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings.

My invention relates to improvements in the slack-thread spring and the parts associated with it; and it consists in certain features of construction and in combinations of parts hereinafter described, and pointed out in the claims.

In the drawings, Figure 1 is an end view of the end of the overhanging'arxn of a sewingmachine head on'which the parts constituting my invention are supported. Fig. 2 is a rear view of the end of said arm. Fig. 3 is an enlarged end View of the parts constituting my invention when a part of the outer tension-plate is broken away. Fig. 4 is an enlarged sectional view on line 4 4 of Fig. 3. Fig. 5 isa sectional view of the plate I on line 5 5 of Fig. 3, and Fig. 6 is a horizontal sectional view of the said tension-plate.

Referring to the parts by letters, A represents the hollow front end of the overhanging arm of a sewing-machine head. It is of the usual construction and supports in the usual manner certain well-known parts of a sewing machine, notably the presser-bar B and the reciprocating needle-bar C. Its end plate a also supports the tension device for the upper thread, which device, as herein shown, is in its general construction substantially like that which is shown and described in Letters Patent No. 521,075, dated June 5, 1894; but the outer tension-plate herein shown and indicated by D differs in form from that shown in said prior patent, and therein indicated by I, the form herein shown being expressly contrived to permit the slack-thread spring to be constructed and connected with the machine and to perform its funtion substantially as hereinafter described. This plate D has a curved slot d, as shown in said prior patent, and at opposite ends of this slot in the part cl of this plate are the backwardly-cut notches or recesses d (1 The part (1 of this plate to the right of this slot is that part by which the desired tension is applied to the thread. In other words, it is substantially like the corresponding part of the outer tension-plate of said prior patent. The thread passes into the recess 01 under the tension part of the plate d, out through the recess W, and thence through the eye in the end of the slack-threadcontrolling spring. D to the left of this slot is, however, bent outward, or, in other words, it lies in a plane in front of the plane in which the tension part at of this plate lies. When, therefore, this plate D is connected to the end plate aof the -arm"A in substantially the manner shown in spring may project from beneath the left end of the plate through the slot d to a position outside the right or tension end of this plate,

where it may be engaged by the upper thread T. This slack-thread spring is made of wire and has at one end a coil e, which lies upon a serrated disk F, having a central aperture f, through which a screw H passes, by which it is rotatabiy held against the plate a. There is a notch f in this disk, and this notch receives the rearwardly-turned end 6 of the coil 6. The other end of this spring is straightened out to form an arm e, which is of such length that it passes from beneath the left end of the plate D and extends a short distance beyond the slot at. This arm 6 is provided at its extremity With an eye e for the thread to pass through, which eye has, preferably, an

-opening and is therefore specifically a hook.

The tension of this spring-arm is downward; but its downward movement is limited by a finger g, which projects through a slot ct in the end plate a, which finger is formed in the end of one arm of a bell-crank lever G, pivoted to the rear side of said plate a. Just inside of the head of the screw H, upon which the serrated disk is mounted, there is a crown-spring washer h, which bears upon the inner part of the coil and applies sufficient pressure to the disk F to hold it in any position to which it may be moved, while permitting it to be The part (i of the platemoved into any position desired. Obviously by turning this disk the tension of the springarm 6 will be increased or diminished, depending upon the direction in which the disks turn. When the machine is threaded, the thread T after passing through the tension device is passed through the hook e on this slack-thread spring E, then through an eye in the end of the movable take-up arm J, and thence down to the needle. During one complete reciprocation of the needle the thread will be tightened by the operation of the takeup arm J and the spring-arm 6 will be drawn upward. Then the thread will be slackened, and this slack is taken up by the downward movement of this slack-thread springarm e. The slack-thread spring is made of very thin wire, as shown, and when it is moved to its upper position by the tightened thread is liable to be worn and cut by said thread. To prevent such action as far as possible, a small rib d is formed on or attached to the plate D in the path of the end of this spring-arm, the front side of this rib being in a plane in front of the spring-arm. The thread slides over this rib after passing through the hook of said spring, and therefore when the end of the spring gets close to this rib the pull of the thread is outward over the rib and the spring-arm is relieved very materially from the pressure and wear of the thread.

Sewing-machines are adapted to sew material of different thicknesses. The thicker the material the higher is the presser-foot b, which rests upon it. It is desirable that the slack-thread spring shall cease its takingup action at about the time the needle enters the material. It is desirable, therefore, that the slackspring shall cease its said action earlier when thick material is in the machine than when thin material is in it. This result is attained by means of the finger g, by which the downward movement of the spring-arm e is stopped and by mechanism which causes the said finger to be moved upward proportionately with the upward movement of the presser-foot. As shown, this spring 6 is so lifted by means of the bell-crank lever G, before referred to, the horizontal arm 9 of which has the finger g formed thereon. The substantially vertical arm g of this bell-crank lever is provided with a slot 9 whose lower end is inclined, and into this slot a pin 1), which is fast on the presser-bar, projects. The raising of the presser-bar B therefore operates this lever G, which lifts the slackthread spring, thereby slackening up the thread. WVhen the presser-bar is moved downward, the bell-crank lever is moved in the reverse direction, whereby the spring is allowed to move downward to a lower point.

Having described my invention, I claim- 1. In a sewing-machine, a slack thread spring comprising a coil, whose inner end is bent backward, and an arm with a hookshaped extremity and means for guiding the thread, combined with a disk having a central hole in which is a notch which receives the inner bent end of the coil, a stud which is secured to the end plate of the machinearm and which passes through said disk and coil, a crowned springwasher which embraces said stud outside of said coil, and means for applying the pressure to the out side of said spring, substantially as and for the purpose specified.

2. In a sewingmachine, a slack-thread spring-arm secured to the end of the machinearm and having its tension downward and having at its extremity an eye for the thread, combined with a bell-crank lever whose vertical arm has an inclined slot and whose other arm has a finger which projects beneath said spring-arm, the presser-bar, and a pin which is secured thereto and enters said slot, substantially as and for the purpose specified.

3. In a sewing-machine, a tension-plate having a curved slot with backwardly-extended recesses at its ends, said plate on one side of said slot being in a plane in front of the tension part of the plate on the other side of said slot, combined with a slack-thread spring-arm secured to the machine-arm behind the forwardly-bent part of said plate and extending through said curved slot and over the tension part of said plate and having at its extremity an eye for the thread, substantially as and for the purpose specified.

4.. In a sewing-machine, a tension-plate having a curved slot with backwardly-extended recesses at its ends, said plate on one side of said slot being in a plane in front of the tension part of the plate on the other side of said slot, combined with a rotatable disk located behind the forwardly-bent part of said plate, a slack-thread spring having a coil which is located between said disk and plate and having at its extremity an eye for the thread, and has its inner end secured to said disk, and having also a spring-arm which projects through said curved slot to a posi tion outside of the tension part of said plate and having at its extremity an eye for the thread, and a spring-clamping device for holding said disk against rotation, substantially as and for the purpose specified.

5. In a sewing-machine, a tension-plate having a curved slot with backwardly extended recesses at its ends, said plate on one side of said slot being in a plane in front of the tension part of the plate on the other side of said slot, combined with a slack-thread spring-arm having at its extremity an eye for the thread secured to the machine-arm behind the forwardly-bent part of said plate and extending through said curved slot and over the tension part of said plate, a rib on said plate above and in the path of the free end of said spring-arm, substantially as and for the purpose specified.

6. In a sewing-machine, a slackthread spring-arm secured at one end to the end of the machine-arm and having a hook-shaped extremity, combined with a rib located above and in the path of said hook-shaped extrem- In testimony whereof I hereunto affix my ity and means for guiding the tbread into signature in the presence of two Witnesses. the hook-shaped extremlty of sald spring- WILLIAM GROTHE arm whereby said thread passing to said hook- 5 shaped extremity passes over and in contact Witnesses:

with said rib, substantially as and for the E. L. THURSTON, purpose specified. E. B. GILCHRIST. 

